Refining of mineral oils



. layers.

Patented Feb. 9, i937 PATENT eerie.

REG or MINERAL ons Malcolm H. Tuttle, New Rochelle, N. Y., assignor to Max B. Miller & Co., Inc., New York, N. Y., a corporation of Delaware Application January 31, 1934, Serial No. 709,098

3 Claims.

combustion engines and the like) and into a naphthenc type oil, by means of a solvent for the former and a solvent or solvents for-the latter. Examples of such processes are disclosed in the present inventors copending application Ser. No. 623,483, filed July 20, 1932 and in his Patent No. 1,912,349, `issued May 30, 1933. The present application is in part a division of said application Serial No. 623,483.

'A feature of the present invention resides in providing for the improvement of the properties of a paramnic type oil in a simple and eflcigt manner.'

More specigiically, a feature of the invention is the provision of a-process of this character in which naphthenic solvent is employed to cause an eicient separation of desired qualityparanic oil from a fraction of lubricating oil already highly parainic in character', and to enable a ready recovery of a largeportion of the naphthenic solvent for reuse without the need for evaporating much of this solvent from the oil.

Another feature of the present process is the production of a paraiiinic type oil having a high viscosity index (arelatively small reduction in viscosity for a given rise of temperature) and an improved color. l

Other objects, features, and advantages of the invention will become apparent as the following detailed description of an example of the present process proceeds, reference being had to the accompanying drawing wherein:

The figure is a diagrammatic How-sheet of a process in accordance with the invention.

With referencetc the flow-sheet, a charge oil to be treated, which may be an overhead distillate, a residual oil, or other mineral oil from which a parainic type oil is to be separated, may be introduced into extraction apparatus oi convenient construction, and may be treated with counterflowing parainic and naphthenic solvents adapted to form solutions which are miscible to but a limited extent so that they tend to separate into For instance, a parafinic solvent, such as a liquefied normally gaseous hydrocarbon (propane or the like) or a liquid hydrocarbon (petroleum ether or the like), may be introduced at the bottom of an extraction tower and a suitable naphthenic solvent, such as commercial cresylic acid, or other known naphthenic solvent,

(Cl. 19E-13) or mixtures of one or more of them with pyridine, furfural, analine, or liquid sulphur dioxide, or the like, may be introduced at the top of the tower, so that the solvents counterow, or in other ,words so that the paraiinic oil fraction or rafnate is washed with naphthenic solvent and the naphthenic oil fraction or extract, removed from the presence of the charge oil, is washed with parafnic solvent.

The operations may be conducted continuously or by batch treatment, and the extraction may be carried out in a series of separate chambers, or repeated, if desired. The amounts of solvents may vary depending upon the nature of oil to be treated, but in general may advantageously be suilicient to readily dissolve their respective oil fractions. The temperature of the mixture is advantageously maintained below the critical temperature at which the solvents become miscible. This temperature varies for diierent solvents but may be readily determined for given solvents. Where normally gaseous solvents are employed, the mixture in the extraction apparatus should be under sufficient pressure to malntain the solvents liquid, and the apparatus is then preferably maintained full of liquid. Any convenient pumps and control devices may be employed for this purpose.

The parainic layer or raiilnate leaving the top of the primary extraction apparatus will contain parailinic type oil, paraiiinic solvent and some entrained or entrapped naphthenic solvent, and the paraimic solvent may next advantageously be removed and returned as indicated for reuse. The removal of the paraflinic solvent may be accomplished by means of an evaporator where the boiling point of this solvent is lower than that of the naphthenic solvent, as is preferably the case. However, it may be removed in other ways if more convenient. A

The parafnic oil and naphthenic solvent passing from the evaporator are next preferably but not necessarily mixed with additional naphthenic solvent and fed to separator where the resulting mixture is allowed to form layers. Upon reducing the ratio of parafiinic solvent to naphthenic solvent, a rather remarkable result is achieved, for the upper layer. will be found to contain by far the major portion of the parafnic oil and markedly less naphthenic solvent than the mixture entering the separator` contained, and the lower layer will contain only a few percent of oil and markedly more naphthenic solvent than was added to the mixture entering this separator.

The upper layer in the separator may then be withdrawn and the naphthenic solvent remaining therein may then be removed as by evaporation. The oil thus produced will be found to have an extremely light color and a high viscosity index, being considerably improved in these respects over the oil resulting from merely removing the solvents from the parainic layer leaving the primary extraction apparatus.

The naphthenic solvent, containing small amounts of oil and forming the lower layer in the separator, is preferably withdrawn from the bottom of the separator and pumped into the primary extraction apparatus as shown, being vsupplemented, if desired, by additional naphthenic solvent pumped from a suitable storage reservoir. The solvent in this reservoir may be supplied principally by naphthenic solvent recovered from the naphthenic oil fraction or extract leaving the primary extraction apparatus and recovered from the parafiinic oil fraction leaving the separator, additional solvent to compensate for losses being added to the storage reservoir as required. Similarly, paraillnic solvent may be recovered from the naphthenic oil fraction leaving the extraction apparatus. Suitable valves may be provided for controlling the proportions of naphthenic solvent fed to the extraction tower and to the mixture entering the separator, or for by-passlng the solvent around the latter, if desired, under certain conditions.

By way of a specic example, a distillate from a San Joaquin crude having a viscosity index of 5l was treated in accordance with the present process with solvents totalling 300% by weight of propane and 800% by weight of creslyic acid,4

based upon the weight of the oil treated, and parafnic oil fraction, amounting to 26% of the oil treated, was produced having a viscosity index of and an N. P. A. standard color of l to 11/2. Moreover, it appears that the viscosity index is increased from about 85 to 100 and that the N. P. A. color shows an improvement of 1 to 1%l points, by virtue of the separation step in which naphthenic solvent is added to the paraiinic fraction and the mixture is permitted to form layers. In addition the yield secured was high, while at the same time the need for evaporating large amounts of solvent was avoided. More specifically, whereas the parainic layer leaving the primary extraction apparatus contained about 50..v

parts of oil to 50 parts of cresylic acid, the upper layer withdrawn from the separator contained about 85 parts of oil and only 15 parts of cresylic acid. Advantages are secured. however, even though this upper layer is composed of only 75 parts of oil and 25 parts of cresylic acid, or even less oil and more acid. On the other hand the lower layer from the separator contained only 3 to 5% of oil. Similar, but possibly somewhat less marked advantages may be achieved with residual oils.

If desired the oil in the separator may be cooled or heated somewhat to promote the separation into layers, though this is not deemed to be essential. It will be apreciated that the evaporation of propane or other liquefied normally gaseous hydrocarbon in the evaporator v'has the eiect of lowering the temperature of the mixture, and

naphthenic solvent.

Through the present development there is provided a simple and efficient process for producing a high grade paraiinic type oil without the need for distilling or evaporating large amounts of solvents. Moreover, the recovered naphthenic solvent is well adapted for direct reuse in the process. The parafnic type oil produced is a good yield of oil having a high viscosity index and an excellent color, in some cases practically water white.4 Moreover, the apparatus required is slmple and emcient, both in construction and in operation.

While the invention has been described in connection with certain features set forth in my patent and application to which reference has been made, and while it has especial advantages when employed in connection with such a process, it may enjoy a more general application and accordingly is not to be limited in its broader aspects save by the appended claims.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described, or portions thereof, but it is recognized that various modiilcatlons are possible within the scope of the invention claimed.

What is claimed is:

1. In the art of refining a mineral oil by means of liquefied propane and a separable naphthenic solvent, the steps comprising counterlowing said propane and solvent in the presence of the oil to be dened, separating from the resulting mixture a ralnate fraction containing oil, propane and solvent, evaporating at least a portion o the propane from said withdrawn raffinate iraction to cause the same to separate into layers, separating the layers thus formed and returning the bottom layer to the rst-named step.

2.1,:111 the art of reilning a mineral oil by means :of separable paramnic and naphthenic solvents,

the steps comprising commingllng said oil with. both of said solvents, separating from the resulting mixture a raiinatL traction containing oil and portions of both of said solvents, reducing the ratiov of paraiilnic solvent to naphthenic solvent by removing at least a portion of the ture a homogeneous ramnate fraction containing oilI paralnic solvent and naphthenic solvent, re" moving at least a portion of said parafiinic solvent from the ranate, to cause the rainate layer to separate into an upper layer and a lower layer containing only a few per cent. of oil and most of the naphthenic solvent of the raffinate, withdrawing said lower layer, and emU ploying the same in the lirst step recited.

MALCOLM H. TUTTLE. 

